docs: def _build_matrix_non_uniform(p, q, coords, k):
      """Constructs the equation matrix for the finite difference coefficients of non-uniform grids at location k"""
      A = [[1] * (p+q+1)]
      for i in range(1, p + q + 1):
          line = [(coords[k+j] - coords[k])**i for j in range(-p, q+1)]
          A.append(line)
      return np.array(A)